Abstract
Sebastiano Serlio, an architect and architectural theoretician in the period of Renaissance, wrote nine books on architecture. These books give us valuable acknowlegde on architecture in that age. His First Book deals with geometry and has a geometrical scheme in the last page of it. He explains it a method of constructing a "porta" in front of architecture in his text. R. Wittkower pointed out it a method of making ratios of 1:2, 1:3 schematically in his famous book on Renaissance architecture. It has been regarded as a method how to decide position of doorway in the facades of architecture. This paper clarifies that Serlio's scheme is not simply a method of constructing a doorway but also a method how to make a city-gate, castle gate and monumental gate and so on (as porta meant primarilly). It is also clarified that it is a fundamental diagram to make ratios that derive from ratios of 1:2, 1:3 and it presumed to be a method how to design facades of Serlio's architecture in this paper.
